Fixation clamp

ABSTRACT

A fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements, has of at least one clamping assembly having at least one reception provided by means of grooves to accommodate a fixation element along the longitudinal axis of the reception. At least one locking element extends through the clamping assemblies for blocking the position of the clamping assemblies in a defined angular position. The clamping assembly comprises a first jaw and a second jaw which are in contact with each other via respective contact surfaces. The clamping assembly comprises at least two orientation devices that extend from and/or into said contact surfaces which at least two orientation devices serve to orient the first jaw with respect to the second jaw.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 13/302,559, filed Nov. 22, 2011, and claims priority fromEuropean Patent Application No. 10 194 945.1, filed Dec. 14, 2010, thedisclosures of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a fixation clamp and, moreparticularly, to a fixation clamp for use in an external fixation systemfor holding bone fragments adjacent each other. External fixationsystems are widely used to connect two or more bone fragments to eachother. Such systems comprise bone screws, pins, wires which are inserteddirectly into the bone material and these systems use externalstructural elements as fixation rods, bars and rings. In order toconnect the rods and bars to form a rigid frame, fixation clamps areused. Furthermore, fixation clamps are used to connect the screws andpins to the rigid frame to specifically hold bone fragments at anintended place.

One adjustable fixation clamp is known from U.S. Pat. No. 6,080,153comprising two pairs of jaws allowing clamping of a rod as well as of apin.

A clamp for multiple rod-shaped elements is known from U.S. Pat. No.7,618,417 having one single pair of jaws. However, such a clamp allowsclamping more than two, e.g. three or four rod-shaped elements as pinswith one single clamp, thus reducing the number of clamps. However, onefurther fixation clamp is necessary to fix the rod of said clamp to theframe of the fixation system.

U.S. Patent Application Publication No. 2006/0287652 mentions that usualfixation clamps as e.g. known from U.S. Pat. No. 6,080,153 allowclamping of one single screw or pin to the frame. This way of attachingpins or rods leads to bulky fixation systems. Therefore 2006/0287652discloses a fixation clamp addressing this problem and comprises twopairs of jaws within which each pair of jaws allows the introduction andclamping of two rods or pins etc. at the same time.

These clamps according to the prior art either provide differentdiameters of the reception openings provided by the jaws to introducedifferent sizes of rods, pins or wires, or they rely on additionalinserts as e.g. disclosed in U.S. Publication 2008/0065068. Such insertsreduce the diameter of the reception cavities to allow a secure fixingof differently sized rods, pins or wires.

From U.S. Publication 2010/0298827 a further fixation clamp is known.The disclosure of U.S. 2010/0298827 is incorporated herein by reference.Users feel very comfortable with the fixation clamp according to thisdesign. However, past use has shown that in some applications the jawsof the clamping assembly have been orientated in an erroneous mannerwhich led to unsatisfactory results. Hence there is a need to have afixation clamp with which erroneous alignment of the jaws is prevented.

SUMMARY OF THE INVENTION

It is one aspect of the present invention to provide a fixation clampwhich overcomes the disadvantages of prior art. It is in particular oneaspect of the present invention to provide a fixation clamp with whicherroneous alignment of the jaws is prevented. Furthermore such afixation clamp shall be adjustable during the mounting process to alarge degree.

Such an aspect is achieved by the features of claim 1. Accordingly afixation clamp, more particularly for use in an external fixation systemfor holding bone fragments adjacent to each other with the help offixation elements, comprises at least one clamping assembly having atleast one reception provided by means of grooves to accommodate afixation element along the longitudinal axis of the reception. At leastone locking element extends through the clamping assemblies for blockingthe position of the clamping assemblies in a defined angular position.This clamping assembly comprises a first jaw and a second jaw which arein contact with each other via respective contact surfaces. The clampingassembly comprises at least two, preferably exactly two, orientationdevices that extend from and/or into the contact surfaces which at leasttwo orientation devices serve to orient the first jaw with respect tothe second jaw.

The arrangement of at least two orientation devices has the advantagethat a misalignment of the jaws can be prevented. Furthermore the jawswill be positioned with an enhanced accuracy. In case the clampingassembly is designed such that a pivoting motion between the clampingassembly and the locking element becomes possible, the arrangement ofthe at least two orientation devices is also very advantageous tocompensate possible misalignments during the mounting process.

The orientation device comprises preferably an opening extending fromsaid surface into the respective jaw and a protrusion extending fromsaid surface away from the respective jaw wherein said protrusionengages in the opening. Hence one of the jaws comprises the openings andthe other jaw comprises the protrusions. Alternatively it is alsopossible to mix the openings with the protrusion on one of the jaws,namely to arrange a protrusion and an opening on a first jaw and anopening and a protrusion on a second jaw.

The openings have preferably the shape of a channel or slot extendingalong an axis which is substantially parallel to the plane of thesurface. The slot or channel has the advantage that the width of theslot or channel can be varied for several purposes.

Preferably the protrusions extend in direction of the central axis ofthe locking element and the axis of the channel extends substantiallyperpendicular to the central axis, wherein the protrusion engages intothe channel perpendicular to the axis of the channel.

Preferably the channel opens out into neighboring grooves. Thereby thechannel is accessible from two sides which is advantageous for cleaningpurposes. In this case the sidewalls of the channels serves as abutmentelement for the protrusion. Hence the protrusion engages with thesidewalls of the channels.

Alternatively the channel can also be limited on the opposite side ofone of the grooves as viewed along the respective axis of the channel byan abutment element, which abutment element has a surface which ispreferably curved around a central axis extending perpendicular to therespective surface. Here the abutment element as well as partly thesidewalls serve as abutment element for the protrusion.

A first channel extends preferably along a first axis being parallel tothe surface and a second channel extends along a second axis beingparallel to the surface, wherein the first axis is angularly arranged tothe second axis.

The protrusions have preferably the shape of pins preferably with acircular cross-section. The protrusions and the openings are arrangedsuch that the first jaw and the second jaw are connectable in only onedetermined aligned position.

Preferably the orientation devices are provided such that rotation ofthe first jaw with respect to the second jaw is prevented. Alternativelythe orientation devices are provided such that rotation of the first jawwith respect to the second jaw is permitted in a narrow field ofrotation such as rotation angle in the range of 0.5° to 5° beforeblocking the clamping assemblies by means of the locking element.

Further embodiments of the invention are set forth in the dependentclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the followingwith reference to the drawings, which are for the purpose ofillustrating the present preferred embodiments of the invention and notfor the purpose of limiting the same. In the drawings,

FIG. 1 shows a perspective view of a first embodiment of a fixationclamp of the present invention;

FIG. 2 shows a cross-section of the fixation clamp according to FIG. 1;

FIG. 3 shows a top view of the fixation clamp for FIG. 1;

FIG. 4 shows a perspective view of a washer that is used in the fixationclamp of FIG. 1;

FIG. 5 shows a side view of a clamping assembly of the clamping elementof FIG. 1;

FIG. 6 shows a cross-sectional view along line X-X of FIG. 5;

FIG. 6A is the cross-sectional view of FIG. 6 showing an alternate slotor channel design;

FIG. 7 shows a perspective view of a first jaw of the clamping assemblyof FIG. 5;

FIG. 8 shows a top view of the jaw of FIG. 7;

FIG. 9 shows a side view of the jaw of FIG. 7;

FIG. 10 shows a perspective view of a second jaw of the clampingassembly of FIG. 5;

FIG. 10A is the perspective view of FIG. 10 showing the alternate slotor channel design of FIG. 6A;

FIG. 11 shows a top view of the jaw of FIGS. 10; and

FIG. 11A is the top view of FIG. 11 showing the alternate slot orchannel designs of FIGS. 6A and 10A.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a preferred first embodiment of a clamping element orfixation clamp 10 pursuant to the invention. The clamping element 10consists of a first clamping assembly 20 and a second clamping assembly30 and a locking element or shaft 40 which is positioned through bores21, 31 within the two clamp assemblies 20, 30 along the longitudinalaxis M of shaft 40. The shaft 40 is preferably a locking element adaptedto allow closing the clamp assemblies 20 and 30. Shaft 40 enters a firstjaw 11 through a washer 41.

The shaft 40 comprises a head portion 44, a reduced diameter portion 43which is followed by a shaft portion 42 and a thread portion 49. Theouter threaded portion 49 is adapted to be screwed into a complementaryinner thread within the distal jaw 11 a so that turning the head of theshaft 40 changes the longitudinal position of the shaft 40 against thelower jaw 11 a, which allows opening or closing the entire clamp 10against the force of a spring 15 provided between the two clampassemblies 20 and 30. Spring 15 is preferably positioned incorresponding counter bores 16 and 16 a in jaws 12 and 12 arespectively. Instead of spring 15, provided around shaft 40, it ispossible to provide a different spring means as Belleville washers or anelastic compressible solid or foam. Upon closing of the clamp assemblies20 and 30 the jaws 12, 12 a adjacent to the spring 15 can eventuallycome into contact and then the anti-rotation surfaced 55 which areprovided in both surfaces of the jaws 12, 12 a fix the angularorientation of each clamping assembly 20 and 30 against the other.

Preferably after having mounted the shaft 40 with the thread 49 withinthe lower jaw 11 a, the end portion of the thread 49 is destroyedthrough pressure to ensure that the shaft 40 cannot be removed from theclamping assemblies 20, 30 to maintain the clamp as one single piece.

Each clamping assembly 20 or 30 comprises two opposing clamping jaws 11,12 and 11 a, 12 a. These jaws 11, 11 a and 12, 12 a are essentiallysimilarly shaped on the sides facing each other. Each of the jaws 11,12, and 11 a, 12 a comprises a respective contact surface 18, 19 and 18a, 19 a facing the other surface of the jaw 11, 12 and 11 a, 12 a.

In order to prevent rotation between jaw 11, 11 a and jaws 12, 12 a aswell as in order to prevent a misalignment of the jaws 11, 12 and 11 a,12 a at least two orientation devices or anti-rotation devices 13, 14 isarranged on the surfaces 18 a, 19 a. In the present embodiment in thesecond clamping assembly 30 the jaw 11 a comprises an opening 14extending into surface 18 and the jaw 12 a comprises a pin 13 extendingfrom surface 19. The pin 13 extends into the opening 14. Thispin-opening connection prevents therefore a possible rotation betweenthe jaws 11 a, 12 a and a possible misalignment between the jaws 11 a,12 a. This will further be outlined in more detail with FIGS. 5 to 11.

The jaws 11 and 12 are provided here with three grooves 51, 52 and 53.Jaws 11 a, 12 a have similar grooves 51 a, 52 a and 53 a however onlythe grooves of jaws 11 and 12 will be described. Grooves 51, 52 and 53are all provided in a same plane perpendicular to the longitudinal axisof shaft 40. In that plane they are oriented perpendicular to the radialdirection from the center of the bore 21 or 31. As such the grooves 51,52 and 53 are substantially parallel to outer side wall 61, 62 or 63 ofeach pair of jaws 11 and 12.

Each pair of grooves 51, 52 or 53, respectively, in each jaw 11 and 12,define one reception, i.e. a first reception 71, a second reception 72and a third reception 73. The grooves 51, 52 and 53 are each formed as arounded semi-spherical recess in section to provide receptions 71, 72and 73 which accommodate cylindrical pins or rods with a defineddiameter, if the clamp is closed. The outer side walls 61, 62 or 63 cancomprise an inclined sliding surface to allow an easier clipping of suchpins or rods 100 into the corresponding reception. The grooves 51, 52,53 form rounded semi-spherical recesses in a section. This means thatthe recesses provided by the grooves 51, 52, 53 have a hollowcylindrical shape to accommodate rod-shaped elements. Some or all of thegrooves 51, 52, and 53 are also provided with friction enhancingelements such as ribs 56.

All three grooves 51, 52 and 53 have different sizes so that thecorresponding receptions 71, 72 and 73 have three different sizes. Inother words each reception 71, 72 or 73 is adapted to accept a differentfixation element, i.e. a rod, screw, pin or wire having a differentdiameter. One preferred embodiment of the first clamping assembly 20 hasgrooves to accept fixation elements having a diameter of 12 mm, 8 mm and5 mm, respectively. A different embodiment may have a sequence ofdiameters of 8 mm, 6 mm and 4 mm, respectively.

The second clamping assembly 30 according to the embodiment of FIG. 1also comprises two jaw portions 11 a and 12 a and these comprise threegrooves 51 a, 52 a, 53 a. These grooves 51, 52, 53 also comprise asequence of different sizes. These grooves four receptions 71 a, 72 aand 73 a having outer walls 61 a, 62 a and 63 a. In the embodiment shownthe inner jaw portions 12, 12 a have an identical structure as have theouter jaws 11, 11 a especially in view of the anti-rotation device 55,the counter bore 16 for a spring 15.

Within a preferred embodiment the first clamping assembly 20 maycomprise a sequence of smaller sizes, e.g. 7 mm, 5 mm and 3 mm; or 6 mm,5mm and 4 mm; and the second clamping assembly 30 may comprise asequence of larger sizes, e.g. 13.5 mm, 12 mm and 10 mm. Different sizesare possible, usually for wires starting from 2 mm diameter untilthicker rods with a diameter of 30 mm are used within such a clamp 10.Such a clamp 10 allows using one single versatile clamp, wherein thefirst clamping assembly 20 is used to fix a specific pin or screw orwire having a diameter for which one of the receptions 71, 72 or 73 isadapted. The user takes the clamp 10 and orients the first clampingassembly 20 into the correct alignment so that the pin or screw can beclipped into the corresponding reception.

Then the clamp 10 can be clamped on a rod of an external fixator withthe help of the second clamping assembly 30. Second clamping assembly 30can be oriented in a way so that the rod can be clipped into thecorresponding reception. It is an advantage of the clamp 10 having twoclamping assemblies 20 and 30 according to the invention, that apractitioner attaching such a clamp to a bone screw with one clampingassembly 20 and subsequently a rod of an external fixator to the otherclamping assembly 30 can check the robustness of his external fixator,and if he finds that the rod he has used is not stiff enough, he simplyopens the second clamping assembly 30, removes the thinner rod, turnsthe second clamping assembly 30 e.g. 60 degrees into one direction orthe other around the longitudinal axis to align the larger receptionwith the new thicker rod and replaces it. This change does notnecessitate the replacement of the clamp 10 itself as necessary withprior art systems. The method to replace such a rod is faster and morereliable since the clamping of the bone screw is not changed, and avoidsuse of a second sterile clamp at said time.

It is of course also possible that the second clamping assembly 30 is atraditional clamping assembly or even any other element known in theprior art with clamping elements. The object of a versatile clampingassembly is already achieved through one first clamping assembly 20,since it allows clamping one of three different sizes of screws, pins ofwires through simple reorientation of the first clamping assembly 20.

FIG. 2 shows a cross-section of the clamp according to FIG. 1, whereinthe clamp 10 is shown in a premounted state, i.e. the spring 15 is undertension. The upper jaw 11 of the first clamping assembly 20 is thereforepushing the washer 41 against a flange 45 of the head of shaft 40. Thebore 21 which accommodates part of the shaft portion 42 and the reduceddiameter portion 43 is provided with a larger diameter than therespective diameter of the shaft 40 so that an angular or pivotingmovement of the first clamping assembly 20 against the shaft 40 ispossible. This is in particularly advantageous during the mountingprocess of the fixation clamp. With this regard it has to be noted thatalso bore 31 can be provided with a larger diameter than the respectivesection of the shaft 40 such that jaw 12 of the second clamping assemblybecomes pivotable to the shaft 40.

The diameter D1, D2 of bore 21 of the first clamping assembly 20 islarger than the diameter of the locking element 40 extending through thebore 21. Thereby a pivoting movement or displacement between the lockingelement 40 and the first clamping assembly 20 during positioning theclamping assemblies 20, 30 and the pins or rods becomes possible. In thepresent embodiment the bore 21 in the first jaw 11 is a bore 21 havingan abutment surface 86. The abutment surface 86 is provided by means ofa step-like bore 21 having a first section with a first diameter D1 anda second section with a second diameter D2. The first diameter D1 islarger than the second diameter D2. The abutment surface 86 serves asabutment element for the locking element 40 in particular for the flange45 in case washer 41 is removed. Hence the abutment surface 86 togetherwith the flange 45 prevents that the first clamping assembly 20 from thesecond clamping assembly 30 when the washer is removed. Particularlyduring a cleaning or sterilization process the prevention of such aseparation is very advantageous.

Alternatively the bore 21 can be provided with a conical section 32 asshown with bore 21 in the jaw 12 of the first clamping assembly. In thepresent embodiment there are two conical sections arranged, whereby thediameter of the bore 21 decreases with increasing length of the bore asseen from outside of the jaw 12. In case two conical sections 32 arepresent the degree of pivoting motion can be increased.

The shaft 40 as part of a locking element is threaded into the lower jaw11 a of the second clamping assembly 30. Hence the lower jaw 11comprises a threaded opening. Threading may be provided in the bore orthe screw may exhibit self-tapping threading. Quite generally, a lockingelement may be provided which may be a lever locking element or abayonet lock. Among these locking elements may also be supporting disksor toothed disks, which, for the sake of simplicity, are not shown inthe drawings.

Therefore the two clamp assemblies 20, 30 can be opened and closedthrough turning the head of shaft 40 and thus turning said shaft 40 inthe jaw thread.

In the cross-sectional view of FIG. 2 it can also be seen that thelocking element 40 extends through the first clamping assembly 20 and isin contact with the second clamping assembly 30 by means of the threadedportion 49. In mounting position in which the rods or pins will bepositioned in the receptions 71, 72, 73 the first clamping assembly 20is moveable along the middle axis M of the threaded portion 49. Uponactuation of the locking element 40 the first clamping assembly 20 willbe moved against the spring pressure towards the second clampingassembly 30 such that the anti-rotation surface 55 of the first clampingassembly 20 comes into contact with the respective anti-rotation surface55 of the second clamping assembly 30. Once the locking element 40 isfirmly tightened the first clamping assembly 20 and the second clampingassembly 30 are in contact with each other via the anti-rotation surface55.

In FIG. 2 the mounting position of clamping assemblies 20, 30 is shown.Thereby the clamping assemblies 20, 30 are positioned at the distance toeach other with regard to the middle axis M. The second clampingassembly 20 is in contact with the locking element 40 and the spring 15pushes the first clamping assembly away from the second clampingassembly 20 towards the washer 41 which is contact with the flange 45 ofthe locking element.

To summarize: The clamping assemblies 20, 30 will be moved due toactuation of the locking element 40 from a mounting position to alocking position and afterwards when fixation shall be cancelled fromthe locking position to the mounting position. After use the washer 41will be removed as explained below in order to sterilize the clampingelement 10 for further use.

FIG. 3 shows a view from above on the clamp according to FIGS. 1 and 2.Since the embodiment of FIG. 1 comprises three grooves 51, 52 and 53,there are three side walls 61, 62 and 63, which provide, when lookedfrom above as in FIG. 2 a triangular shape of each clamping assembly 20or 30.

With the aid of FIGS. 5 to 11 the at least two orientation devices oranti-rotation elements 13, 14 will now be explained in the following.While described in connection with clamping assembly 30 they may be alsoprovided on clamping assembly 20. In principle the orientation devicesserve to provide a help for the user to align a first jaw 11 withrespect to a second jaw 12. Once the orientation devices 13, 14 engagewith each other they also serve as anti-rotation devices to preventunwanted rotation between the jaws 11, 12. In the following the term“orientation device” is used for the sake of simplicity.

The orientation device 13, 14 comprises an opening 14 extending intosaid surface 18 a, 19 a and a protrusion 13 extending from said surface19 a, 18 a wherein said protrusion 13 engages in said opening 14. Sinceat least two of the orientation devices 13, 14 are arranged there are atleast two protrusions 13 and at least two openings 14. Preferably thenumber of protrusions 13 is equal to the number of openings 14. In thepresent embodiment exactly two orientation devices 13, 14 are arranged.

In the present embodiment the protrusions 13 extend from the surface 18a of the first jaw 11 a and the openings 14 extend from the surface 19 aof the second jaw 12 a into the latter. It is also possible to arrangethe protrusions on the surface 19 a of the second jaw 12 a and theopenings 14 from the surface 18 a in the first jaw 11 a. It is furtherpossible to arrange one protrusion 13 and one opening 14 on/in the firstjaw 11 a and to arrange one protrusion 13 and one opening 14 on/in thesecond jaw 11 a.

The openings 14 according to FIGS. 6 and 10 to 11 have the shape ofchannels or slots 14 extending along respective axes 140, 142. The axes140, 142 extend substantially parallel to the plane of the contactsurface from which the channels 14 extend into the jaw, here to thecontact surface 19 a.

The protrusions 13 have the shape of pins 13 preferably with a circularcross-section. Pins 13 then engage into channels or slots 14.

The protrusions 13 according to FIGS. 6 to 9 extends in a direction ofthe middle axis M of the locking element 40. The axis 140, 141 ofchannels 14 extends substantially perpendicular to middle axis M sincethe contact surfaces 18 a, 19 a extend also substantially perpendicularto the middle axis M. The protrusions 13 engage into channels 14perpendicular to said axis 140, 141 of the channels 14.

In the present embodiment there are arranged at least two, (exactly twoare shown), channels 14. A first channel 140 extends along a first axis141 being substantially parallel to surface 19 a and a second channel142 extends along a second axis 143 being substantially parallel tosurface 19 a. The first axis 141 is arranged angularly to second axis143. Preferably the angle between the first axis 141 and the second axisis in the range of 60 to 120°, more preferably the angle issubstantially a right angle of 90°.

The first axis 141 or the channel 140 extend substantially perpendicularto the direction of a neighboring groove 51 a. The term direction of agroove is to be understood as the direction of a middle axis thatextends along the groove.

The second axis 143 or the channel 142 extends angular, preferably withan angle in the range of 30° to 60°, in particular with an angle of 45°,to the direction of a neighboring groove 51 a.

At least one of the channels, here both channels 140, 142 open out intoa neighboring groove 51 a, 52 a and are limited on the opposite side ofthe groove 51 a, 52 a as viewed along the respective axis 140, 142preferably by an abutment element 144. In other embodiments as shown inFIGS. 6A, 10A and 11A, it may also be possible to omit the abutmentelement such that a channel is provided which extends from a firstgroove to a second groove. Hence such a channel then opens out in twogrooves. However, the abutment element 144 has advantages in view of theaccuracy of the orientation between the jaws 11 a, 12 a. Nevertheless ithas to be noted that an open channel 140, 142, even if it is open on oneend only has advantages concerning the sterilization process as thefluid enters the channel also via grooves 51 a, 52 a.

The abutment element 114 has a surface which is preferably curved arounda middle axis extending perpendicular to the respective surface 18 a, 19a.

With regard to the arrangement of the pins 13 and the channels 14 it hasto be mentioned that they are arranged such that the first jaw 11 a andthe second jaw 12 a are connectable in only one determined alignedposition such that a misalignment becomes impossible.

Furthermore the orientation devices 13, 14 are provided such thatrotation of the first jaw 11 a with respect to the second jaw 12 a isprevented.

Alternatively the orientation devices 13, 14 are provided such thatrotation of the first jaw 11 a with respect to the second jaw 12 a ispermitted in a narrow field of rotation. A narrow field of rotation canbe defined as a rotation angle in the range of 0.5° to 5°. However sucha rotation shall only be permitted during the mounting process of thefixation clamp, i.e. before blocking said clamping assemblies 20, 30 bymeans of the locking element 40. In order to allow such a rotation, thechannels 14 and pins 13 are provided with respective tolerances. Hencethe channel 14 can be provided with a larger width such that the pin 13is able to move with respect to the channel 14. The pin 13 then abuts atthe sidewalls limiting the channel 14. The sidewall are the wallslimiting the channel this extending from the surface 18 a, 19 a into thejaw.

The depth of the opening 14 from the surface 18 a, 19 a along the middleaxis M of the locking element is preferably larger than the length ofthe protrusion 13 in the same direction. This configuration ensures thatthe surfaces 18 a, 19 a are always in full contact with each other.

The protrusion 13 can also be provided with a chamfered edge 130allowing a better insertion of the protrusion into the opening.

Furthermore the orientation device 13, 14 allows better positioning ofthe jaws 11 a, 12 a with respect to each other. In particular the jawsmay move slightly in a floating manner with respect to each other whichenables a self-centering function once the pin or rod has beenintroduced into the respective reception 71 a, 72 a, 73 a.

Reference is now made to FIGS. 1 to 4. In the present embodiment thefirst clamping assembly 20, here jaw 11, comprises a first contactsurface 80 which is in contact with a second contact surface 81 of thewasher 41. The washer 41 and the first clamping assembly 20 are incontact via contact surfaces 80, 81. The contact surfaces 80, 81 arespherical having the same curvature radius such that the washer 41 isenabled to slide with respect to the first clamping assembly 20 on thecontact surface 80 when it comes to the above mentioned pivoting motionof the first clamping assembly 20 with respect to the locking element40. The curvature is at least the same over an overlapping surface whichhere is defined as the surface which encompasses the maximal glidingmotion of the washer 41 on the contact surface 80.

In the present embodiment the first contact surface 80 has a convexshape, whereas the second contact surface 81 has a concave shape. Such aconfiguration is particularly advantageous as it allows a pivotingmotion as mentioned above while providing a very compact structure ofthe fixation clamp in terms of axial and radial dimension. Furthermorethe surfaces which are shaped as explained allow that the washer 41 asexplained in detail below is removable from the clamping element 10.Thereby the first clamping assembly 20 and the second clamping assembly30 become loose such that the parts are slightly moveable along middleaxis M and sterilization of the clamping element 10 is possible withoutdemounting or disassembling the clamping element 10 completely. This isvery advantageous since during sterilization the parts remain togetherand re-assembly of the parts afterwards is not necessary. Hence theparts of the clamping element 10 remain loosely together such that thesterilization fluid is able to enter clearances between the respectiveparts. As mentioned above providing the diameters D1 and D2 accordingly,the abutment surface 86 serves as element which holds the parts looselytogether.

The first contact surface 80 of the first clamping assembly 20 extendsfrom a section point 82 between the middle axis M of the locking element40 and said first contact surface 80 towards the first clamping assembly20.

FIG. 3 shows the clamping element from above. In FIG. 3 the overlappingsurface with limiting edges 54 can be recognized.

FIG. 4 shows the washer 41 in a perspective view and in FIG. 2 across-sectional view of the washer 41 is shown. In the following thestructure of the washer 41 will be explained.

The washer 41 comprises as mentioned above the contact surface 81 and anupper surface 88 which is arranged at a distance from the contactsurface 81. A central through opening 84 having a middle axis M1 that isat least partly circumvented by means of a sidewall 85. Said throughopening extends from contact surface 81 to the upper surface 88. Thelocking element 40 extends through the through opening.

The sidewall 85 is interrupted by cutout 87 which extends radially tothe middle axis M1 through the sidewall 85 to the opening 84 such thatthe sidewall 85 becomes interrupted. The cutout 87 has a width which isslightly larger than the reduced diameter portion 43 of the lockingelement 40 such that the washer 41 can be moved radially to the lockingelement 40 in order to remove the washer 41 after the use of theclamping element 10. The width is defined as the clearance of the cutout87 from the surfaces 89 of the sidewall limiting the cutout.

Furthermore the washer 41 comprises a recess 83 extending along middleaxis M1 from an upper surface 88 which is arranged opposite the contactsurface 81. The recess 83 is designed to accommodate the flange 45 ofthe locking element 40. The recess 83 can also be designated as abutmentelement since it prevents the washer from being radially displaced tothe middle axis M of the locking element 40. In order to demount thewasher 41 it is necessary to push the first clamping assembly 10 towardsthe second clamping assembly, such the washer 41 can also be moved alongthe middle axis M of the locking element 40. Thereby the flange 45 willbe moved out of the recess 83. Once the flange 45 has been moved suchthat there is no connection between the flange 45 and the recess 83, thewasher 41 can be moved radially to the locking element 40 whereby theshaft of the locking element will pass the cutout 87 of the washer.

Recess 83 extends from the upper surface 88 along the middle axis M1 ofthe through opening 84 into the washer 41. The washer is preferably madeout of a metallic material.

To summarize the arrangement of the contact surfaces 80, 81 has theadvantage that during the mounting process of the fixation clamp 10 apivoting motion of the first clamping assembly becomes possible with alarge deflection. Furthermore the removable washer 41 has the advantagethat the clamping assemblies 20, 30 become moveable along theinterlocking element 40 such that an effective sterilization becomespossible.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1-26. (canceled)
 27. A fixation clamp for use in an external fixationsystem for holding bone fragments adjacent to each other with the helpof fixation elements, said fixation clamp comprising: at least oneclamping assembly, and at least one locking element extending throughthe at least one clamping assembly for blocking the position of the atleast one clamping assembly in a defined angular position; wherein saidclamping assembly comprising: a first jaw having a contact surface andat least one groove; a second jaw having a contact surface and at leastone groove, the second jaw contact surface is in contact with thecontact surface of the first jaw; at least one reception provided bymeans of said grooves to accommodate a fixation element along alongitudinal axis of the reception; at least two orientation devicesthat extend from and/or into said contact surfaces, the at least twoorientation devices are adapted to orient the first jaw with respect tothe second jaw, wherein the orientation device comprises an elongaterecess extending from one of said contact surfaces into the respectivejaw and a protrusion extending from the other of said contact surfacesaway from the respective jaw, wherein said protrusion engages in saidelongate recess, wherein the elongate recess has the shape of a channelor a slot extending along an axis which is substantially parallel to aplane of the surface wherein the protrusion extends in the direction ofa middle axis of the locking element and said axis of said channel orslot extends substantially perpendicular to said middle axis, whereinsaid protrusion engages into said channel perpendicular to said axis ofthe channel and wherein said channel or slot opens out into twoneighboring grooves, forming an open channel.
 28. The fixation clampaccording to claim 27, wherein a first channel extends along a firstaxis being parallel to said surface and a second channel extends along asecond axis being parallel to said surface, wherein the first axis isangularly arranged to said second ax1s.
 29. The fixation clamp accordingto claim 27, wherein the first axis or the channel extends substantiallyperpendicular to the direction of a neighboring groove.
 30. The fixationclamp according to claim 27, wherein the second axis or the channelextends angular, preferably with an angle in the range of 30° to 60°, inparticular with an angle of 45°, to the direction of a neighboringgroove.
 31. The fixation clamp according to claim 27, wherein the firstaxis and the second axis extend angular with an angle of 60° to 120° toeach other, preferably substantially perpendicular to each other. 32.The fixation clamp according to claim 27, wherein the protrusions havethe shape of pins preferably with a circular cross-section.
 33. Thefixation clamp according to claim 27, wherein the protrusions and theopenings are arranged such that the first jaw and the second jaw areconnectable in only one determined aligned position.
 34. The fixationclamp according to claim 27, wherein the orientation devices areprovided such that rotation of the first jaw with respect to the secondjaw is prevented or wherein the orientation devices are provided suchthat rotation of the first jaw with respect to the second jaw ispermitted in a narrow field such as rotation angle in the range of 0.5°to 5° before blocking said clamping assemblies by means of the lockingelement.
 35. The fixation clamp according to claim 27, wherein betweensaid locking element and said at least one clamping assembly there isarranged a washer and wherein said clamping assembly comprises a firstcontact surface which is spherical and convex and in that said washercomprises a second contact surface which is spherical and concave,wherein the first contact surface is in contact with the second contactsurface.
 36. The fixation clamp according to claim 27, wherein theclamping assembly comprises a bore through which said locking elementextends, wherein said bore comprises a diameter that is larger than thediameter of the locking element in the respective region that theclamping assembly and/or parts of the clamping assembly is pivotableagainst the locking element and/or wherein the bore comprises at leastone conical section such that the clamping assembly is pivotable againstthe locking element.
 37. A fixation clamp for an external fixationsystem comprising: a first and a second jaw member respectively havingfirst and second facing contact surfaces each including first and secondgrooves angled with respect to one another, and having alignable throughbores; a shaft extending though the bores in the first and second jawmembers and the first and second contact surfaces; means for moving thefirst and second contact surfaces along the shaft towards one another;and first and second recessed openings formed in the first jaw member,each recessed opening open to the first contact surface and first andsecond protrusions on the second jaw member extending outwardly from thesecond contact surface and movable into the respective first and secondrecessed opening by said means for moving the first and second contactsurfaces towards one another wherein the first recessed opening is achannel or slot that extends completely along a linear first axis thatis parallel to the plane of the first contact surface and opens out intothe first and second grooves, and the second recessed opening has theshape of a channel or slot that extends completely along a linear secondaxis parallel to the plane of the first contact surface and opens outinto the first and second grooves, wherein the first axis extends at anangle to said second axis and wherein the first axis and the second axisextend angularly with an angle of 60° to 120° to each other.
 38. Thefixation clamp according to claim 27 wherein the protrusions andrespective channels or slots engage such that rotation of the first jawwith respect to the second jaw is permitted in a narrow field such asrotation angle in the range of 0.5° to 5° before blocking said clampingassemblies by means of the locking element.
 39. A fixation clamp for usein an external fixation system for holding bone fragments adjacent toeach other with the help of fixation elements, said fixation clampcomprising: at least one clamping assembly having a bore therethrough,and at least one locking element extending through the bore of the atleast one clamping assembly for blocking the position of the at leastone clamping assembly in a defined angular position; wherein saidclamping assembly comprising: a first jaw having a contact surface withfirst and second grooves; a second jaw having a contact surface withfirst and second grooves, the second jaw contact surface is in contactwith the contact surface of the first jaw, when the first and secondgrooves on the first and second jaws are aligned; two receptions areprovided by means of said grooves to accommodate a fixation elementalong a longitudinal axis of the reception; first and second orientationdevices that extend from and/or into respective said contact surfaces,the first and second orientation devices are adapted to orient the firstjaw with respect to the second jaw and wherein the first and secondorientation devices are provided such that a rotation angle of the firstjaw with respect to the second jaw is permitted in the range of 0.5° to5° before blocking said clamping assemblies by means of the lockingelement wherein the first orientation device is an elongate slotextending between an opening into the first and second grooves which alot includes a surface engaging the second orientation device to providethe rotation angle; and wherein the elongate slot completely extendsalong a linear axis which is substantially parallel to the contactsurface.
 40. The fixation clamp according to claim 39, wherein betweensaid locking element and said at least one clamping assembly there isarranged a washer and wherein said clamping assembly comprises a firstcontact surface which is spherical and convex and wherein said washercomprises a second contact surface which is spherical and concave,wherein the first contact surface is in contact with the second contactsurface.
 41. The fixation clamp according to claim 39, wherein theclamping assembly comprises a bore through which said locking elementextends, wherein said bore comprises a diameter that is larger than thediameter of the locking element in the respective region that theclamping assembly and/or parts of the clamping assembly is pivotableagainst the locking element and/or wherein the bore comprises at leastone conical section such that the clamping assembly is pivotable againstthe locking element.